Antimicrobial and antibiofilm effects of selenium nanoparticles on some foodborne pathogens

Microbial biofilms, which characterized by their resistance to the traditional antimicrobials, are considered as a renewable source of contamination by pathogens. As alternative antimicrobial and antibiofilm agent selenium nanoparticles (SeNPs) were biosynthesized by treatment of 1 mM SeO2 with the free-cell supernatant of Bacillus licheniformis isolated from food wastes. The biosynthesized SeNPs were characterized by their spherical shape with diameter range of 10-50 nm and a well-defined absorption peak at 263 nm in UV-vis spectra. The biosynthesized SeNPs were used to control growth and biofilm formation by six foodborne pathogens including Bacillus cereus, Enterococcus faecalis, Staphylococcus aureus, Escherichia coli O157:H7, Salmonella Typhimurium, and Salmonella Enteritidis. The MIC90 of SeNPs against all tested bacteria was 25 μg/mL, whereas the antibiofilm concentration was 20 μg/mL against all bacteria, except B. cereus. Although the biogenic SeNPs had antimicrobial and antibiofilm effects, they did not show ability to remove the established biofilm up to 50 μg/mL. The concentration of 75 μg/mL showed slight effect on removing the established biofilm. No toxicity on Artemia larvae was demonstrated by SeNPs upto 100 μg/mL. In conclusion, SeNPs produced in the present study can be used as a promising agent for effectively preventing biofilm formation by foodborne pathogens.